JP4686896B2 - Manufacturing method of electret processed product - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an electret processed product, and more particularly to a method for manufacturing an electret processed product for producing a high-quality and high-performance electret processed product.
[0002]
[Prior art]
Conventionally, an electret-processed fiber sheet has been used as an air filter material excellent in low-pressure loss. As a conventional method for producing this electret fiber sheet, a method of applying a high voltage to a fiber sheet such as a synthetic fiber nonwoven fabric and electretizing it by corona discharge (see Japanese Patent Application Laid-Open No. Sho 61-102476, etc.), film A method is known in which a high voltage is applied to a sheet by a wire electrode, and the film is electretized by corona discharge, and then the film sheet is made into a non-woven fabric (see Japanese Patent Publication No. 57-14467).
[0003]
However, in each of the above conventional methods, a polymer material sheet is placed on the ground electrode, a needle-like or wire electrode is placed close to the surface, and a DC high voltage is applied between both electrodes. Since it is an electret by corona discharge, unevenness is likely to occur due to adjustment of the gap accuracy between the earth electrode and the applied electrode, resulting in uneven charging, and damage to the sheet due to spark discharge, etc. There was a problem.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a method of manufacturing an electret processed product that eliminates the above-described problems of the prior art and enables production of high-quality and high-performance electret processed products.
[0005]
[Means for Solving the Problems]
The manufacturing method of the electret processed product of the present invention that solves the above-described problem is to immerse the non-conductive sheet in a pressure vessel filled with water, pressurize the water to infiltrate the non-conductive sheet, and then the non-conductive sheet In the manufacturing method of the electret processed product which dries the porous sheet into an electret , the water is selected from ion-exchanged water, distilled water or reverse osmosis membrane filtered water, and the pressure vessel is filled with water. The inside of the pressure vessel is depressurized and the non-conductive sheet is deaerated before being filled .
[0006]
In order to immerse the non-conductive sheet in a pressure vessel filled with water in this way, pressurize the water and infiltrate it, so that the pressurized water permeates evenly to every corner inside the non-conductive sheet Can do. Therefore, by drying this, a high-quality, high-performance electret processed product having a high and uniform charge density can be obtained.
[0007]
In the above water permeation treatment for the non-conductive sheet, if the non-conductive sheet is degassed in advance, it becomes possible to distribute water evenly to the inside, and further, high quality and high performance. It can be an electret processed product.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The non-conductive sheet used in the present invention is not particularly limited as long as it is a non-conductive material. For example, fiber sheets such as woven fabrics, knitted fabrics, and nonwoven fabrics of synthetic fibers or natural fibers, or plastic film sheets can be used. Among these, a synthetic fiber sheet is particularly preferable. Further, in the case of an air filter, a synthetic fiber nonwoven fabric is preferable, and in particular, for a high performance filter, it is preferable to use a melt blown nonwoven fabric.
[0009]
The material of the nonconductive sheet is not particularly limited as long as it is a nonconductive material. Preferably, a material having a volume resistivity of 10 ¹² · Ω · cm or more, more preferably 10 ¹⁴ · Ω · cm or more is mainly used.
[0010]
Examples thereof include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polylactic acid, polycarbonates, polystyrenes, polyphenylene sulfites, fluororesins, and mixtures thereof. Among these, those mainly composed of polyolefin or polylactic acid are preferable from the viewpoint of electret performance, and those mainly composed of polypropylene are more preferable.
[0011]
The non-conductive sheet used in the present invention preferably contains at least one of a hindered amine additive and a triazine additive. By including such an additive in the non-conductive sheet, it is possible to maintain a particularly high electret performance with respect to the non-conductive sheet.
[0012]
Of the above two types of additives, the hindered amine-based additive may be poly [((6- (1,1,3,3, -tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl. ) ((2,2,6,6, -tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6, -tetramethyl-4-piperidyl) imino)] (manufactured by Ciba Geigy, Chimasorp 944LD ), Dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (manufactured by Ciba Geigy, Tinupin 622LD), 2- (3,5-di- t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) (manufactured by Ciba-Geigy, Tinupin 144) It is.
[0013]
Examples of the triazine-based additive include the aforementioned poly [((6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl) ((2 , 2,6,6, -tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6,6, -tetramethyl-4-piperidyl) imino)] (manufactured by Ciba-Geigy, Chimersoap 944LD), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) -phenol (manufactured by Ciba Geigy, Tinupin 1577FF), etc. Among these, particularly hindered amine System additives are preferred.
[0014]
The amount of hindered amine-based additive or triazine-based additive added to the non-conductive sheet is not particularly limited, but is preferably in the range of 0.5 to 5% by weight, more preferably 0.7 to 3% by weight. % Range is good. If the addition amount is less than 0.5% by weight, it is difficult to obtain the desired high level electret performance. Moreover, when it mix | blends so much that it exceeds 5 weight%, it is unpreferable since it will worsen a spinning property and film forming property, and will also become disadvantageous also in cost.
[0015]
In addition to the above additives, the non-conductive sheet is added with known additives generally used for non-conductive sheets of electret processed products such as heat stabilizers, weathering agents, polymerization inhibitors, etc. Also good.
[0016]
In the present invention, as water to be permeated for electretization of the non-conductive sheet, it is important to use water that has been cleaned as much as possible by removing dirt with a liquid filter or the like . In particular, it is important to use any one selected from pure water such as ion exchange water, distilled water, and reverse osmosis membrane filtered water . The purity of pure water is preferably 10 ³ μS / m or less in terms of conductivity, more preferably 10 ² μS / m or less.
[0017]
What added the water-soluble organic solvent to the said water can be used. This is because the water permeability to the non-conductive sheet can be further improved by adding the water-soluble organic solvent. As the water-soluble organic solvent, those having a boiling point lower than that of water are preferable. That is, since the water-soluble organic solvent is added to improve the water permeability to the non-conductive sheet, it is preferable to vaporize and dry it as soon as possible once water has penetrated the sheet. More preferably, a water-soluble organic solvent having a boiling point difference with water of 10 ° C. or more is preferable.
[0018]
The type of the water-soluble organic solvent is not particularly limited as long as it improves the water permeability to the non-conductive sheet. For example, alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, ketones such as acetone and methyl ethyl ketone, esters such as propyl acetate and butyl acetate, other aldehydes and carboxylic acids can be used. In particular, alcohols or ketones are preferable, and it is particularly preferable to use at least one of acetone, isopropyl alcohol, and ethanol. More preferably, the main component is isopropyl alcohol.
[0019]
The concentration of the water-soluble organic solvent with respect to water is not particularly limited as long as it has the effect of improving the permeability, but is preferably 3 to 15% by weight. In particular, in the case of isopropyl alcohol, the range of 3 to 10% by weight is preferable.
[0020]
In the present invention, the treatment for infiltrating water into the non-conductive sheet is performed in the water filled in the pressure resistant container and the water is in a pressurized state. By making water into a pressurized state, the water permeability to the non-conductive sheet is improved, and the water can be permeated so as to be uniformly distributed to every corner of the non-conductive sheet. Therefore, the non-conductive sheet after the drying process can be made into a high-performance electret processed product.
[0021]
The pressure applied to the filled water is preferably in the range of 0.1 to 5.0 MPa, and more preferably in the range of 0.5 to 3.0 MPa. If the pressurization pressure is lower than 0.1 MPa, it is difficult to make the difference from the case of no pressurization remarkable. Even if the pressure is higher than 5.0 MPa, the water penetration effect on the non-conductive sheet is almost saturated, and energy is wasted.
[0022]
In a non-conductive sheet is infiltrated with water which is under pressure, it is important to keep deaerated previously nonconductive sheet under reduced pressure. By performing the deaeration treatment in this way, when the nonconductive sheet is immersed in pressurized water, the water permeation effect can be performed more efficiently. In the deaeration process, the container may be decompressed before water is filled in the same pressure vessel. In the case of continuous treatment, a step of deaeration treatment may be provided in advance before the nonconductive sheet is continuously introduced into the pressure vessel filled with pressurized water.
[0023]
The non-conductive sheet after the water permeation treatment is then electretized in a state where the surface is charged when dried. Any conventionally known method can be applied as the drying method. For example, methods such as a hot air drying method, a vacuum drying method, and a natural drying method are applicable. Among these, the hot air drying method is preferable because continuous processing is possible.
[0024]
In the case of the hot air drying method, the drying temperature needs to be a temperature that does not deactivate the electret. Preferably it is 120 degrees C or less, More preferably, it is 100 degrees C or less, More preferably, it is good to set it as 80 degrees C or less. Moreover, efficient drying can be performed if excess water is removed by nip roll, a water absorption roll, suction suction, etc. as preliminary drying before hot air drying.
[0025]
FIG. 1 illustrates an apparatus for infiltrating water into a non-conductive sheet in the method of manufacturing an electret processed product of the present invention.
[0026]
In FIG. 1, 1 is a pressure vessel, 2 is a water tank in which water W for osmosis treatment is stored, and 3 is a pump for supplying and pressurizing water.
[0027]
The pressure vessel 1 is provided with a platform 4 having a support surface made of a perforated plate or a metal mesh, and a stacked body 60 in which a large number of non-conductive sheets S are stacked is installed on the platform 4. . In addition, an intake pipe 5 is connected to the pressure vessel 1, and the intake pipe 5 is connected to a negative pressure source (not shown) via an on-off valve 51. In addition, the pump 3 supplies the water W in the water tank 2 to the pressure vessel 1 side through the water suction pipe 31 and the supply pipe 32 and further pressurizes after the water is filled.
[0028]
Using the above apparatus, the water permeation treatment for the non-conductive sheet S is performed as follows.
[0029]
For the non-conductive sheet S, for example, a melt blown nonwoven fabric of synthetic fibers is used, and preferably a blend of a hindered amine additive and / or a triazine additive is used. As the water W, pure water is used, and an aqueous solution to which a water-soluble organic solvent such as isopropyl alcohol is added is preferably used.
[0030]
First, the laminated body 60 of the nonconductive sheet S is placed on the platform 4 in the pressure resistant container 1 that has not been filled with the water W yet. Next, the pressure-resistant container 1 is sealed, the on-off valve 51 is opened, and the inside of the container is depressurized by a negative pressure source. By this pressure reduction, the air contained in the non-conductive sheet S in the laminate 60 is degassed.
[0031]
When the deaeration process of the non-conductive sheet S is completed, the on-off valve 51 is closed, and then the pump 3 is operated to supply the water W in the water tank 2 to the pressure vessel 1. The supply of water by the pump 3 is continued even after the pressure vessel 1 is filled with the water W, the water in the filled state is pressurized, and the pressurized pressure is in the range of 0.1 to 5.0 MPa. Maintain in the range of 30 seconds to 120 minutes.
[0032]
As described above, when the water W in the pressure vessel 1 is in a pressurized state, the water W easily penetrates into the non-conductive sheet S that has been degassed in advance, and further increases due to the subsequent pressure. Water permeates evenly to every corner of the interior.
[0033]
After completing the water permeation process in a pressurized state for a certain time, the water is drained from the pressure-resistant container 1, the non-conductive sheet S is taken out, and it is dried. When this drying process is completed, the non-conductive sheet S is in an electret state with a large amount of charge on the surface. The drying method may be any of the methods described above.
[0034]
FIG. 2 shows another embodiment in which water is permeated into the non-conductive sheet. Although FIG. 1 shows the case where the non-conductive sheets in the single wafer state are stacked and processed, FIG. 2 illustrates the case where the non-conductive sheet S is processed as the roll body 61.
[0035]
The non-conductive sheet S is a roll body 61 wound up in multiple layers around the core 6, and the roll body 61 is placed on the platform 4. Other configurations are the same as those in FIG. 1, and the infiltration operation may be performed in the same manner.
[0036]
The core 6 of the roll body 61 is made of a tube material, and the tube material preferably has a porous wall surface. Since the wall surface of the core 6 has a porous structure, the water W can be permeated from the inside of the roll body 61, so that the permeation into the non-conductive sheet can be improved.
[0037]
In each embodiment mentioned above, the deaeration process is not necessarily required. However, by providing this deaeration process step, it becomes possible to distribute water evenly to every corner of the inside of the non-conductive sheet, and it is possible to make the electret processed product of higher quality and higher performance. .
[0038]
【Example】
The characteristic values used in the examples described below are measured by the following measuring method.
[0039]
[Collection performance]
It measured with the collection performance measuring apparatus shown in FIG. In this collection performance measuring apparatus, a dust storage box 12 is connected to an upstream side of a sample holder 11 for setting a measurement sample M, and a flow meter 13, a flow rate adjusting valve 14, and a blower 15 are connected to a downstream side. In addition, a sample holder 11 is provided with a perch counter 16, and the pert counter 16 is used to measure the number of dusts on the upstream side and the number of dusts on the downstream side of the measurement sample M via the switching cock 17. Can do.
[0040]
In measuring the collection performance, polystyrene standard latex powder having a diameter of 0.3 μm is filled in the dust storage box 12, the sample M is set in the holder 11, and the air flow rate is adjusted to 6.5 m / min. Adjusted with the flow rate adjustment valve 14, the dust concentration is stabilized in the range of 10,000 to 40,000 pieces / 2.83 × 10 ⁻⁴ m ³ (0.01 ft ³ ), and the number of dusts D upstream of the sample M and the number of dusts d downstream. Was measured 10 times with a particle counter 16 (manufactured by Lion Co., Ltd., KC-01B), and the collection performance (%) was determined by the following formula based on JIS K-0901.
[0041]
Collection performance (%) = [1- (d / D)] × 100
Where d: number of downstream dusts D: number of upstream dusts [average fiber diameter]
The fiber diameter was measured for 100 fibers enlarged by SEM photographs, and the average value was determined.
[0042]
Example 1
A melt-blown nonwoven fabric having a melt index MI of 700 and a polypropylene added with 1% of a triazine-based additive (Ciba Geigy, Kimaribe 944) as a raw material and having a basis weight of 40 g / m ² and an average fiber diameter of 2.0 μm by a normal melt-blowing method Manufactured.
[0043]
The above melt-blown nonwoven fabric is subjected to a permeation treatment under the following conditions using reverse osmosis membrane filtered water as water for permeation using the apparatus of FIG. 1, and then dried with hot air at 80 ° C. for 20 minutes after draining. Thus, an electret melt blown nonwoven fabric was obtained.
[0044]
Degassing treatment: Depressurized pressure −98 kPa, treatment time 2 minutes Osmosis treatment: Pressurization pressure 3.0 MPa, pressurization time 5 minutes The collection performance of the electret meltblown nonwoven fabric obtained as described above was measured. It was a very high level of 9997%.
[0045]
Reference example 1
In Example 1, an electret meltblown nonwoven fabric was obtained by impregnation treatment and drying treatment under the same conditions as in Example 1 except that the deaeration treatment was not performed.
[0046]
When the collection performance of this electret meltblown nonwoven fabric was measured, it was a high level of 99.997%.
[0047]
Comparative Example 1
The same melt blown nonwoven fabric as in Example 1 was used as a raw material, and an application treatment was performed at a high voltage (+25 kV) with a high voltage application device.
[0048]
It was 99.6% when the collection performance of the obtained melt blown nonwoven fabric was measured, and was a low level compared with Example 1 and Reference Example 1 .
[0049]
【The invention's effect】
As described above, according to the present invention, in order to infiltrate the non-conductive sheet in the pressure vessel filled with water and in a pressurized state, the pressurized water is evenly distributed to every corner inside the non-conductive sheet. By being able to permeate so as to be distributed, a high-quality, high-performance electret processed product having a high and uniform charge density can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a permeation treatment apparatus used in the method for producing an electret processed product of the present invention.
FIG. 2 is a schematic view showing another example of a permeation treatment apparatus used in the method for producing an electret processed product of the present invention.
FIG. 3 is a schematic view showing a collection performance measuring apparatus used in an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pressure-resistant container 2 Water tank 3 Pump 4 Mounting stand 5 Intake pipe 60 Laminated body 61 (of nonelectroconductive sheet) Roll body S (nonelectroconductive sheet) Nonconductive sheet

Claims (8)

A method for producing an electret processed product, wherein a non-conductive sheet is immersed in a pressure vessel filled with water, the water is pressurized and permeated into the non-conductive sheet, and then the non-conductive sheet is dried and electretized. In this case, as the water, any one selected from ion-exchanged water, distilled water or reverse osmosis membrane filtered water is used, and the inside of the pressure vessel is depressurized before the pressure vessel is filled with water. manufacturing method of an electret processed product you characterized in that degassing treatment sexual sheet. The method for producing an electret processed product according to claim 1 , wherein the permeation treatment is performed in a state where the non-conductive sheet is rolled up. The method for producing an electret processed product according to claim 1 or 2, wherein the pressure applied to the water is 0.1 to 5.0 MPa. The electret processed product according to any one of claims 1 to 3 , wherein 0.5 to 5 wt% of at least one of a hindered amine additive and a triazine additive is blended in the non-conductive sheet. Method. The method for producing an electret processed product according to any one of claims 1 to 4 , wherein the non-conductive sheet is a synthetic fiber sheet. The method for producing an electret processed product according to claim 5 , wherein the synthetic fiber sheet is a melt blown nonwoven fabric. The method of manufacturing an electret processed product according to any one of claims 1 to 6 , wherein the non-conductive sheet is mainly composed of polyolefin. The method for producing an electret processed product according to claim 7 , wherein the polyolefin is mainly composed of polypropylene.

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